There has been proposed an image discrimination apparatus which divides an image signal into parts in units of each shot by detecting cut points of the image, and which discriminates an important shot from the plurality of shots.
As a process of detecting cut points, there is a method of detecting, as cut points, points at each of which the brightness of the image changes between adjacent frames and the difference in the brightness between the frames is larger than a fixed threshold, as disclosed by, for example, the following nonpatent reference 1.
Furthermore, as disclosed in the following nonpatent reference 2, there is a method of evaluating a difference between frames using an evaluation function and detecting, as cut points, points at each of which the difference between frames is larger than a threshold which is preset by learning other image contents.    [Nonpatent reference 1] Nikkei electronics No. 892 2005.1.31, pp. 51    [Nonpatent reference 2] “Shot Change Detection from Partially Decoded MPEG Data”, the Institute of Electronics, Information and Communication Engineers paper magazine Vol. J81-D2 No. 7 (July, 1998), written by Yasuyuki Nakajima, Kiyono Ujihara, Akio Yoneyama, published by the Institute of Electronics, Information and Communication Engineers, pp. 1564 to 1575.
Because the conventional image discrimination apparatuses are constructed as mentioned above, while points at each of which the brightness of the image changes between adjacent frames and the difference in the brightness between frames is larger than a fixed threshold are detected as cut points, a problem is that because the threshold is fixed even though any kind of image signal is inputted, the accuracy of the detection of cut points degrades.
Another problem is that because in the case of using the threshold which is preset by learning other image contents, the learned results change according to the contents which are learning objects, cut points cannot be correctly detected unless the contents which are applied to an image signal inputted are learned, and therefore the method cannot be used for general purposes.
The present invention is made in order to solve the above-mentioned problems, and it is therefore an object of the present invention to provide an image discrimination apparatus which can detect cut points correctly even when any kind of image signal is inputted.